Process for the coagulation of castilloa latex



Patented Dec. 18, 1945 PROCESS FOR THE COAGULATION F CASTILLOA LATEXTirey Foster Ford, Arlington, Va., assignor to the United States ofAmerica, as represented by the Secretary of Agriculture N 0 Drawing.Application August 31, 1943, Serial No. 500,649

2 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'700. G. 757) This application is made under the act of March 3, 1883, asamended by the act of April 30, 1928, and the invention hereindescribed, if patented, may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment to me of any royalty thereon.

This invention relates to the coabulation of Castilloa latex which inits natural state is normally stable when treated with acids, and hasamong its objects a process or the coagulation of such latex in a simplemanner.

Hevea rubber latex is readily coagulable by acid substances and suchcoagulation is an essential step in most commercial methods of preparingHevea rubber. Similar methods cannot be used with Castilloa latex.Commercial development of Castilloa rubber has been retarded by thedifiiculty and uncertainty of the primitive methods now in use incoagulating its latex.

I have found that Castilloa latex can be coagulated by acid substancesand salts used for coagulation of Hevea latex, provided the Castilloalatex is first treated with dilute ammonia, caustic soda, or otheralkaline substances, and in the case of acid substances such are used insuflicient quantity to neutralize the alkaline substance and coagulatethe rubber. Gentle heating is necessary to produce rapid andsatisfactory coagulation and clumping of the rubber, but the heating canbe at any time during or after addition of the alkaline and acidsubstances or salts.

Although the mechanism of the treatment is not known, probably itseffect is to dissolve substances other than rubber from the surfaces ofthe latex particles. So long as these substances, which are probablyproteins, coat the particles, they cause the particles to be positivelycharged, and, therefore, to be uncoagulated by positive ions. Removal ofthese substances by the alkaline substance does not of itself producecoagulation, be cause negative rubber particles remain, which, likeHevea latex particles, are stabilized by alkaline substances. Like Hevealatex particles, however, they are now coagulable by acid substances andsalts used for coagulation of Hevea latex.

I have also found that use of certain alkaline substances, includingalkaline salts such as trisodium phosphate and sodium carbonate, andeven sodium hydroxide and ammonium hydroxide, can produce coagulationalone. In the use of sodium hydroxide, however, coagulation occurs onlywithin a narrow concentration range and is less satisfactory than theresults which can be obtained by additional use of an acid substance.

otherwise, ar illustrative of the process of coagulaticn of thisinvention.

Example I A mixture of the sample of latex and 1 cc. of 10 percentaqueous NHz did not coagulate in the cold, gave a grainy, non-coherentcoagulum on gentle heating, but addition of 1.3 cc. of 18 percent I-IClimmediately produced a good compact coagulum. Using /2 cc. of theammonia and /2 cc. of the H01 gave a coherent co'agulum on boiling, andusing /3 cc. of the ammonia and cc. of the H01, gave a coherent coagulumwith several minutes boiling.

Example II A mixture of the sample of latex and 1 cc. of 10 percentNaOl-I gave no coagulum in the cold or on warming. Addition of 1 cc. of18 percent HCl to the heated mixture immediately produced a coagulumwhich was coherent and of good texture. Similar results were obtained byrepeating the process, except that the heating was accomplished afterthe treatment with thehydroxide and the acid.

Instead of using H01, good results were also obtained by using 1 cc. of10 percent H2804, 2 cc. of 10 percent acetic acid, or 1 cc. of 10percent HsPOn Coagulation was also produced by using 1 cc. of 10 percentformic acid, but the coagulum was grainy.

Example III A mixtur of the sample of latex and 1 cc. of 10 percent NaOHgave no coagulum in the cold or on warming. On adding 10 cc. of 10percent NaCl, a coagulum was obtained which was only loosely coherent. Acompact, though grainy, coagulum was obtained by substituting 2 cc. of10 percent CaClz for the NaCl.

The salts mentioned above when used alone did not produce coagulation.

Example IV A mixture of the sample of latex and 2 cc. of

10 percent Na:PO4 gave on heating a grainy, noncoherent coagulum.Addition of 1 cc. of 10 percent HCl and Slight boiling produced clumpingof this coagulum. A mixture of the sample of latex and 2 cc. of 10percent NazCO3 gave on heating a loose coagulum.

Heating the untreated latex or boiling it alone did not producecoagulation. Neither was coagulation produced by making the latex onlyslightly alkaline and then slightly acid, using litmus papers asindicators, even when followed by long heating.

Having thus described my invention, I claim:

1. A process for coagulating Castilloa latex comprising treatinguntreated Castilloa latex with dilute NH40H in the ratio of about 15parts of the latex to from /3 to 1 part of the hydroxide and then withabout to 1.3 part dilute HCl, and heating to facilitate coagulation ofthe rubber.

2. A process for coagulating Castilloa latex TIREY FOSTER FORD.

